Abstract:

Lake Victoria holds a young but species-rich assemblage of cichlid fishes, which form a monophyletic assemblage with additional species from
surrounding water bodies, termed the Lake Victoria superflock. Lake Victoria is surrounded by smaller lakes that are somewhat disconnected
from the main lake. Lake Kanyaboli is such a small lake, having markedly reduced species diversity, in part comprised of Lake Victoria species
and endemics. Here, we studied the modern haplochromine component of the cichlid fauna, represented by Lipochromis maxillaris, Astatotilapia
nubila, Xystichromis phytophagus and Astatotilapia sp. Bigeye, as well as a number of unidentified modern haplochromine specimens. We used
landmark-based geometric morphometrics to study the degree of morphological divergence among those young entities. Twenty landmarks and
14 interlandmark distances were used for shape analysis. Multivariate analysis revealed significant differences between all four species, but
principal component analysis and canonical variate analysis did not clearly discriminate between A. nubila and X. phytophagus, demonstrating
great overall morphological similarity despite clear dietary differences. Besides coloration there was sexual dimorphism in body proportions, so
that only male individuals were analysed further. In all four species, the observed similarities and differences in body shape conform to the type of
ecological specialization of the fish. Most unidentified specimens overlapped the range of A. nubila and X. phytophagus, while the assignment test
based on the canonical variate analysis suggested 70% of the three overlapping entities as separate units. To test their reproductive distinctness
and to demonstrate potential hybridization, nuclear genetic data are needed.